Numerical Investigation of Scour around a Cylindrical Pier in Laboratory Scale and Effect of Collar on Reduction of Scour Using Euler-Lagrange Approach

The placement of a pier causes a three-dimensional complex flow pattern around the pier, which lead to scouring hole around the pier. In this research, modeling of scouring around piers was performed both experimentally and numerically using pimpleLPTdensFoam solver in OpenFOAM. In the first section, two different scenarios were used to simulate the scouring process. In the two numerical models, the effect of phase coupling and drag models on the scoured bed was investigated. One-way coupling with sphere drag model was implemented in the first scenario and four-way coupling with nonsphere drag model in the second one. According to the results, the first model was not satisfying, but the result of the second model was in good agreement with experimental results. The maximum depth of scour at the cross-section in numerical and experimental results was equal (6 percent error). All the simulations were done using the Euler-Lagrange approach and k-w turbulence model to simulate turbulent flow. In the second section of this research, to investigate effective parameters on the reduction of scour, three numerical models including a simple cylindrical pier and two more models using pier with collar were simulated. In order to study the effect of a collar on the reduction of scouring, the simple cylinder without a collar and then with the presence of collar at two different levels were performed. The results show that using collar in level 3.5 and level 4 may respectively lead to 49.2 and 29.7 percent reduction in maximum depth of scour.